While looking for some info on a Google search, I came across an interesting article.
I know this has been bantered back and forth a few times.
Just figured I'd toss it out as another view of that old controversy.


Whale Watching: The Great Tailgate Myth
Driving in a stock pickup with the tailgate dropped won't save gas.

By G.R. Whale
Photography by Truck Trend archives
Truck Trend, June 2005

Someone recently told me about a guy who puts his pickup's tailgate down to save gas. People who follow that practice point to improved fuel-economy figures as proof it helps. Although this may sound like common sense to some, it's a myth: Driving in a stock pickup with the tailgate dropped won't save gas.
We can't blame you for thinking that a flat wall of vertical steel at the back of your truck might present some additional drag, which could hurt fuel economy. However, a raised tailgate doesn't hurt aerodynamics; it helps.
In the old days of blunt-face pickups, most of the wind noise came from the front, but modern trucks draw more noise from wind around the mirrors and exhaust and road noise from behind. Air that circles the cab gets sucked into the bed where it forms a pocket and is for the most part removed from air that flows over the truck. If you've ever had a paper cup or leaves in the bed, as the truck's speed increases, they migrate into the forward corners of the bed and don't get pulled out over the tailgate.
I'm not an aerodynamicist, and I don't have access to the sophisticated equipment and extensive resources to prove this point about airflow, but places like the National Research Council Canada, Ford Motor Company, and DaimlerChrysler do, and they've all come to the same conclusion: Driving with the tailgate down decreases highway fuel economy, and removing the tailgate usually makes it worse. In many instances, it also increases rear lift at speeds, an undesirable condition in a vehicle with only a third of its weight back there to start with.
Putting a tonneau or hard bed cover over your truck is the best thing you can do for highway fuel economy. A shell also can help. Since most of these are relatively light, the extra weight must be worth the improvement. This is one reason something like an Avalanche (which has a bed that's partially covered) often gets better highway mileage than an open pickup with the same drivetrain and tires--and weighs less.
Still not a believer? Ever watch a NASCAR truck race? Don't those pickups run around with covered beds and a small piece of metal sticking nearly straight up? Ever see a land-speed record truck with an open bed? And don't give me that "off-road race trucks have open beds" nonsense. Those beds are little more than sides covering the mechanicals, without a top or bottom, and rear lift is irrelevant when you're 10 feet off the ground.
Also, consider cost. How many manufacturers would cover the cost of making a tailgate standard if it cuts into fuel economy?
Driving gate-down does have its share of increases--in wear. On most pickups, the tailgate adds rigidity to the box, and those prerunner-style pickups usually have an angle bracket from the floor to each side to restore the integrity lost with the lack of a tailgate. On a stock truck, running with the tailgate lowered has a minor impact on the gate hinges, mounts, and cables that support it lowered--they were neither designed nor built as shock-absorbing devices.
So if you want to keep driving around with that tailgate down, that's fine with us--just don't blame us if something goes wrong.

 

I don't do either.......since I have a flatbed

I will swear on a bible that when I had a regular bed truck I gained more mpg's with the tailgate down than up. It was pretty simple for me, save a gas ticket and compare, always made a difference for me. But hey, its just one mans observations.

 

never have either...

Although i need to try this.. and see for myself....

Tx

 

I did an experiment. I filled my truck to the top of the neck, put down my tialgate then got on the highway and didn't stop for 600 miles. I filled up the next morning to the top of the neck again, put up the tailgate, then drove another 600 miles. When I filled up, I compared my mileage and got 2 MPG better with the tailgate up. I left it up for the trip home

 

Exactly!!

Another study was done with bed covers. They found that the only economical change when the FRONT half of the bed was covered, not the bed totally.

Trucks these days are designed in a wind tunnel....these things have been taken into account.

 

Plus if you drive with the tailgate down on gravel roads you will get your paint chipped. Hauling the 4 wheeler alot to hunt hogs proved this to me.

 

I'm with MOAGGIE on this one. Just for the heck of it I put my tailgate down on a 400 mile trip about 2 weeks ago and I picked up about 2 mpg. Could it be because I have 33's on?

 

I saw a research article I think here on dtr a while ago, It had a model truck, a wind tunnel and the various positions of the tailgate. There was less drag when the tailgate was up than when down or removed. The best was when there was a canopy (or cap if you prefer) on the truck bed that sloped from the cab to the rear of the box.

 

I have a bed mounted toolbox on mine. I wonder if that helps the mileage while on the highway, since a post above said covering the front part of the bed helps. Just a thought. By the way, this is a controversial subject, I tried to convince a couple of friends that mileage is better with the tailgate up and a strong argument insued. Of course some people have an opinion and just dont want to be confused with facts.

 

Fact...opinion....who cares. Unless you completely remove it, the possible cost for replacement due to damage while leaving it down doesn't justify any _possible_ savings IMO.

As Kelley said, driving around with it down can present additional chances for chips, dings, and let's not get into what would happen if you were rear ended with the tailgate down.

 

I kept a site filed for about a year showing a dodge single cab and wind tunnel data. I don't all the details but no tailgate was worst, shell a little better, tailgate up better, tailgate down even better, and the best was a cover he made from plywood for the test that extended from the top of the cab to the tailgate that was in a down position. I think those are in the right order.
The kids paper won some award and showed the truck in its different configurations. How he came by the numbers of drag I don't know. Eventually the site didn't work....I lost it.

Sooooooo.....I agree that no tailgate is bad, but lowered tailgate might be better aerodynamics. Shell is a loser too from what I remembered of the paper. Bedcover should be the best practical gainer. I wonder what all this means in mpg's. I doubt much so I just have a toolbox and it gets 20+ hwy.

 

This is really kind of old information. I read some studies done in the early 1980's. I was driving a little Toyota four-cylinder pickup back then, it was so long ago. The conclusion back then was that the tailgate in the up position was better on mpg than no tailgate, down tailgate or installing a flow-through tailgate. Adding a shell or bed cover did nothing to improve mpg and the shell often decreased mpg marginally because of added weight.

 

I saw about 2mpg better with my tailgate down, on my ol' GMC picup. I ran it up most of the time, however.

 

ive got a flatbed too. i dont have to worry about it

 

I've never tried it on the Dodge. But years ago I had an 86 Ford Ranger 4x4 with the 2.9 v6 qnd an auto tranny. with a 2" lift and 30x9.50x15 tires. I put a lot of highway miles on it. Running at 65mph I would get 20-22mpg with tailgate down, 16-20 with it up and 15-17 with it removed. I check my mileage with every tank of fuel on everything I own.